Description: (Applicant's Description) The investigators of Project 1 will assess the chemoprevention of BCCs in BCNS patients. They will test the effects of chemopreventive agents on the development of basal Cell carcinomas (BCCs) in patients with the basal cell nevus syndrome (BCNS). The centerpiece will be a two year randomized double blind clinical trial of the chemopreventive effects of a standardized green tea aqueous extract. We will recruit patients with BCNS, focusing particularly on patients who develop high numbers of BCCs and who live near the participating clinical centers--in New York and San Francisco. We will identify the exact PTC gene mutation carried in each kindred using existing plus novel approaches including a protein truncation test to improve the yield of mutation detection. Subjects will ingest placebo or active agent for two years, and they will be monitored clinically by study investigators at intervals of three months. The end point assessed will be the number of new skin cancers per unit time. Potential toxicity as well as subject compliance (through the assay of tea components in subjects' blood) also will be monitored. One or more additional agents will be tested subsequently as chemopreventives in the same subjects; the selection of these agents will be based on the results of efficacy in trials in murine ptc+/- mice (see Project 2).